Send Broadcast UDP but not receive it on other Android devices

Question

I am trying to develop an app that sends some broadcast messages and receives some answers from the other android devices. I am having some trouble receiving the UDP message

Answer 1

I got this working by using a method described here to calculate the broadcast address: https://code.google.com/p/boxeeremote/wiki/AndroidUDP

Here's my receiver:

try {
  //Keep a socket open to listen to all the UDP trafic that is destined for this port
  socket = new DatagramSocket(Constants.PORT, InetAddress.getByName("0.0.0.0"));
  socket.setBroadcast(true);

  while (true) {
    Log.i(TAG,"Ready to receive broadcast packets!");

    //Receive a packet
    byte[] recvBuf = new byte[15000];
    DatagramPacket packet = new DatagramPacket(recvBuf, recvBuf.length);
    socket.receive(packet);

    //Packet received
    Log.i(TAG, "Packet received from: " + packet.getAddress().getHostAddress());
    String data = new String(packet.getData()).trim();
    Log.i(TAG, "Packet received; data: " + data);

    // Send the packet data back to the UI thread
    Intent localIntent = new Intent(Constants.BROADCAST_ACTION)
            // Puts the data into the Intent
            .putExtra(Constants.EXTENDED_DATA_STATUS, data);
    // Broadcasts the Intent to receivers in this app.
    LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);
  }
} catch (IOException ex) {
  Log.i(TAG, "Oops" + ex.getMessage());
}

And here's my sender:

    public void sendBroadcast(String messageStr) {
    // Hack Prevent crash (sending should be done using an async task)
    StrictMode.ThreadPolicy policy = new   StrictMode.ThreadPolicy.Builder().permitAll().build();
    StrictMode.setThreadPolicy(policy);

    try {
      //Open a random port to send the package
      DatagramSocket socket = new DatagramSocket();
      socket.setBroadcast(true);
      byte[] sendData = messageStr.getBytes();
      DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, getBroadcastAddress(), Constants.PORT);
      socket.send(sendPacket);
      System.out.println(getClass().getName() + "Broadcast packet sent to: " + getBroadcastAddress().getHostAddress());
    } catch (IOException e) {
      Log.e(TAG, "IOException: " + e.getMessage());
    }
  }

  InetAddress getBroadcastAddress() throws IOException {
    WifiManager wifi = (WifiManager) mContext.getSystemService(Context.WIFI_SERVICE);
    DhcpInfo dhcp = wifi.getDhcpInfo();
    // handle null somehow

    int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
    byte[] quads = new byte[4];
    for (int k = 0; k < 4; k++)
      quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
    return InetAddress.getByAddress(quads);
  }